<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Hello Web</title>
  </head>
  <body>
    <style>
      #app {
        display: flex;
        justify-content: center;
      }

      .front {
        font-size: large;
        font-weight: 800;
      }

      .back {
        font-size: large;
        font-weight: 800;
        color: blueviolet;
      }
    </style>
    <div id="app">
      <span class="front">Hello </span><span class="back">World !</span>
    </div>
  </body>
</html>
